Thanks for clearing that up, Oystein.
1. So how would you distinguish between iron and iron oxide spectras? I mean, to me Harrits spectras look mostly like iron oxide with some other ingridients. But how would a spectra of elemental iron look like? Or at least a spectra that could reasonably count as signs of elemental iron?
2. Interesting facts about the alumina. I did not know that. Apparently Harrit either did not look for alumina in the dust samples or did not find any. But did Millette look for it in his dust samples?
One more thing. Have you noticed that on pg. 23 (fig. 24), Harrit compares residues of commercial thermite with residues of red/grey chips. The spectras look pretty much alike to me. Is that because the residues of thermite look like the residues of many things?
1. Relying on XEDS spectra alone is not a good way if you want to be sure. It is possible, with some inaccuracy, to translate the relative heights of the XEDS peaks to relative amounts of the various elements, and then you could compute if there is enough oxygen to oxidize all of the other elements. I have tried that with an XEDS simulation program earlier this year, and it seemed like in one or another of Harrit's spectra, the iron possibley wasn't fully oxidized. But hard to say if it's a mix of elemental iron and Fe
2O
3, or mostly FeO, or simply inaccuracy of data.
The right way to go about it would be to use additional methods that determine the chemical bindings, such as FTIR, PXRD, TEM.
2. Harrit e.al. didn't look for any specific chemical compounds in the paper, they only looked at elemental composition.
Millette did analyse the chemical compounds and found epoxy, iron oxide, al-silicate and titanium oxide, but no Al-oxide or elemental Al.
As for the spectrum of commercial thermite: That's fishy. Fig. 24 shows twice as much Si as Al. This can't be representative of the whole sample, or it is some ****** commercial thermite which the customer should complain about. However spectra like that, with lots of O, Al, Si and Fe, with some C, Na, Mg, K, Ca mixed in, are really totally abundant in all sorts of mineral dust, whether from building construction, industry or nature.